This invention relates to an apparatus for measuring surface defects and more particularly for measuring the depth of surface scratches on the outside of a tube.
Many methods and apparatus have been utilized to follow the profile of a surface and determine the depth of scratches and other defects; however, such apparatus employ mechanical linkage or changes in induction of coils making the apparatus relatively large so that it would be difficult to utilize such apparatus to check the depth of scratches on tubes closely packed in a tube bundle. Another problem that must be solved is the apparatus must fit over a segment of a tube disposed between two support sheets. As the tubes are often scratched while being inserted in the tube bundle and if the tube bundle is a portion of a nuclear steam generator, measuring the depth of the scratches is important for if the scratches are very deep the tubes should be replaced.